I would bet on them being discreet. Good security is very good at making people unaware that security is present. I recall showing my relatives around the Googleplex when I worked there, having my brother-in-law comment on the seeming lack of security for such a high-value target, and then telling him "No, they're there - if you try to walk off with a laptop or take pictures of something you're not supposed to, they'll come running."